There are a bunch of misconceptions and mistaken assumptions about energy that often mislead people into doing things that wind up either causing more problems or costing them more money. The vexing thing about these misconceptions is that at first glance, they seem to make sense. Let’s take a closer look to find out why these misconceptions are groundless and don’t really work in the real physical world.
1. Grounding prongs on 3-way plugs don’t really do anything so you can cut them off.
Some people see the 3 holes in their outlet plugs and think they represent positive, negative, and ground. That’s what they learned in school about how electricity works. It’s a good guess, but it’s wrong.
Household electricity uses Alternating Current (AC), which means that it changes polarity 60 times/second. Because most people learn about DC electrical circuits with positive and negative wires, this detail merely confuses things. Forget about polarity. For our purposes, we’re only looking at the energy streaming into your home. Let’s look at an outlet.
Load is the side of the connection that carries the energy and alternates the positive/negative charge. Think of it a pressurized water line carrying water that switches from blue to red every 60 seconds. It doesn’t matter what color the water is, just that this side carries lots of energy.
Neutral is connected to earth ground and this fixes the voltages to the load side. Neutral must be connected to every light or appliance that load is connected to for the circuit to work. In the breaker box, the neutral wire is connected to the neutral/ground bar. A better word for this wire is “return” because it returns energy to the earth where it is finally neutralized to zero volts…well, safely nearish to zero.
Ground is the safety ground. Ground is connected to the same neutral/ground bar in your home’s breaker box as the neutral wire. The neutral/ground bar is connected to a ten foot metal rod that is driven into the earth.
The important part to remember is that the ground wire has no current running through it. But it’s not useless. Let’s look at case #86-43 from the CDC’s report, Worker Death By Electrocution. Let’s say you’re the restaurant manager who is walking across a freshly wet-mopped floor. You slip and in an effort to keep from falling you grab onto the metal handle of a walk-in refrigerator. Unfortunately, this refrigerator was not plugged into a grounded outlet and somehow the load connection inside the fridge came in contact with the fridge’s metal frame.
Had the refrigerator been connected to ground properly, enough current from the load wire would have been dumped down the grounding wire. Because electricity travels the path of least resistance and grounding wires tie directly to the circuit breaker panel, anytime enough current connects with ground it quickly trips the breaker. Other things and appliances in the kitchen that are safely connected to ground are also in contact with the wet, freshly mopped floor.
Because of the fault, when you grab onto the refrigerator’s handle, you complete the circuit to ground.
Sure, this kind of fatal accident isn’t always the case but without having that third grounding connection to siphon off energy from an electrical fault, you can get badly burned or start a fire. Bottom line: never cut off the ground and replace the plug if it gets damaged.
2. Lightning only strikes from the sky to the ground.
Thunderstorms are some of the most awe-inspiring phenomena we have on this planet. In a classic cloud to ground strike, it appears that a bolt of lightning just smites the ground from on high. And while humans have watched them for millennia and ascribed their power to several gods, it recently turns out that lightning is far more complicated —and way cooler— than anyone ever knew before.
Storm clouds have different layers, and each one can have different charges. During a common cloud to ground strike, a negatively charged arc called a “stepped leader” will creep in 50 yard zig-zagging segments down towards the ground trying to find the route with the least electrical resistance. At the same time, a positively-charged streamer will rise from the earth’s surface —sometimes from a house or a tree. When the streamer and leader connect, the resulting return stroke can transmit billions of watts of electricity upwards. The opposite scenario of a negatively charged stepped leader and positive streamer is also possible. The whole process, however, takes about one-millionth of a second and requires high-speed photography to be seen.
Lightning also causes phenomena high at the top of the atmosphere that extends all the way into space. Blue Jets are cones of electrical energy that occur 25 miles up in the atmosphere. Sprites are red fountain-like features that appear at at the base of the ionosphere descend at up to 6,000 miles per second. And there are Elves, flashes that radiate outwards for up to 200 miles across.
Lightning nevertheless is dangerous and each year causes 4,400 home structure fires. To learn how to protect your home, check out the National Weather Service’s Lightning safety website.
3. Most power spikes come from lightning. A good power strip will protect against it.
Not all power strips have built-in surge protection. Most just have a fuse to keep the power strip from overloading. While fuses take seconds to heat up and fail, voltage spikes or “transient voltages” happen in nanoseconds —one billionth of a second. To protect your electronics, you need a surge suppressor.
While lightning strikes deliver the most transient voltage energy at once, less than one third of all transient voltage surges come from lightning strikes (either nearby or direct hits). Most power spikes and surges originate in your own home because electric motors, lights, and switches in your home sometimes emit a burst of voltage when they are use. These nanosecond-long bursts can reach between “100 to 6,000 volts of peak amplitude lasting from .5 to 2048 microseconds” with current can be as high as 3,000 amps and 90 joules of energy (Jurewicz, R. E. National Power Laboratory Power Quality Study, 1990-1995). Most modern electronics have some sort of buffering circuit built in but these can only take so much punishment and over time, they burn out. Surge suppressors work through a semiconductor called a “Metal Oxide Varister” or MOV. The MOV resists or clamps a transient voltage to a short burst of “let-through voltage” which can be substantially more than the usual household 120 volts. If the incoming voltage goes higher, the MOV suppressor will divert the surge to ground. MOVs are rated in joules in the amount of energy they can absorb by clamping, so the higher the rating the better. Unfortunately MOV suppressors wear out eventually.
If you don’t care for power strips cluttering your floor, another option is a Transient Voltage Surge Suppressor (TVSS) receptacle or outlet. These are outlets hard-wired into an outlet box. TVSS outlets are tough but often when they are surged, you must replace the entire outlet (although replacement modules are available for some). There are also panel-mounted surge suppressors which connect directly into your home’s fuse box. Panel surge suppressors protect all the circuits in your home from surges coming through your power mains— including lightning surges. Costs run from about $25 to hundreds of dollars depending on the clamping capacity as well as your power needs and alarms and indicator lamps. Like other suppressors, once they get zapped, they must be replaced. Panel surge suppressors do not shield your electronics from spikes originating in your home, however, so it is still a good idea to plug your electronics into their own surge protectors.